Water vapor permeability, tensile properties and solubility of methylcellulose-based edible films K. Nazan Turhan a, * , Ferhunde S ß ahbaz b a Department of Food Engineering, University of Mersin, 33332 C ß iftlikk€ oy, Mersin, Turkey b Department of Food Engineering, Hacettepe University, 06532 Beytepe, Ankara, Turkey Received 10 July 2001; received in revised form 14 August 2002; accepted 29 April 2003 Abstract Water vapor permeability (WVP), tensile strength (TS), % elongation (E), adsorption capacity and % soluble matter (SM) were investigated in methylcellulose (MC) films plasticized by polyethylene glycol (PEG). The WVP of films was determined to be 0.232 · 10 10 –1.160 · 10 10 g/m s Pa, TS between 17 and 44 N/mm 2 and %E between 14% and 97%, depending on composition. Film formation was affected by MC concentration, ethanol percent in the solution and the presence of PEG. Incorporation of various molecular weight (MW) PEGs to the polymer matrix increased both WVP and %E, decreased TS. Increase in PEG400 concentration had similar effects. Solubility studies indicated that MC films were water-soluble and PEG containing samples had higher solu- bilities. Results suggest that mainly hydrogen bonding between PEG and MC or blocking effect in the case of high MW PEGs determine the film properties. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Methylcellulose films; Polyethylene glycol; Water vapor permeability; Tensile properties; Film solubility 1. Introduction Shelf life of foods is governed by their numerous in- teractions with their surroundings and can be extended by using protective films. The deterioration of packaged foodstuffs largely depends on the transfers that may occur between the internal environment of the packaged food and the external environment. Edible films can be used to reduce water vapor, oxygen, lipid, and flavor migration between components of multicomponent food products, and between food and the surroundings. Many proteins and polysaccharides have good film- forming properties and can be used in the preparation of edible films (Greener & Fennema, 1994; Martin-Polo, 1995; McHugh & Krochta, 1994; Nisperos-Carriedo, 1994; P erez-Gago, Nadaud, & Krochta, 1999; Torres, 1994; Zagory, 1995). Cellulose-derivative-based edible films are very effi- cient barriers to oxygen and aroma compounds. Water- soluble cellulose derivatives such as methylcellulose (MC) are of interest to researchers because they are able to form a continuous matrix. MC is a cellulose ether that exhibits thermal gelation, forms excellent films, and is used in pharmaceutical and food industries (Donhowe & Fennema, 1993a). MC has been combined with lipids (Greener & Fen- nema, 1989a, 1989b; Kamper & Fennema, 1984; Kester & Fennema, 1989; Koelsch & Labuza, 1992; Rico Pena & Torres, 1990) and polysaccharides (Kester & Fen- nema, 1989; Park & Chinnan, 1995) to make edible films that can serve as effective barriers to water vapor, oxy- gen and carbon dioxide. Polyethylene glycols (PEGs) with various molecular weights (MWs) are effective plasticizers for MC films (Debeaufort & Voilley, 1997; Donhowe & Fennema, 1993b; Park, Weller, Vergano, & Testin, 1993). Several studies were carried out to determine water vapor permeability (WVP), tensile strength (TS) and % elongation (E) of MC-based films. The effects of physical and morphological properties and MW of PEG, tem- perature, ethanol concentration, and film thickness on WVP were investigated (Chinnan & Park, 1995; Journal of Food Engineering 61 (2004) 459–466 www.elsevier.com/locate/jfoodeng * Corresponding author. Address: Department of Food Science, University of Wisconsin-Madison, 1605 Linden Drive Babcock Hall 3B, Madison, WI 53706, USA. Tel.: +1-608-262-2784/+90-324-361- 0001; fax: +1-608-262-6872/+90-324-361-0032. E-mail addresses: knazan@mersin.edu.tr, boyaci99@yahoo.com (K. Nazan Turhan). 0260-8774/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0260-8774(03)00155-9